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    <title>ShellCheck: SC2305 – Quote regex argument to expr to avoid it expanding as a glob.</title>
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    <h1>SC2305 – ShellCheck Wiki</h1>
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    <h2
id="quote-regex-argument-to-expr-to-avoid-it-expanding-as-a-glob">Quote
regex argument to expr to avoid it expanding as a glob.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2305.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> <span class="st">&quot;</span><span class="va">$input</span><span class="st">&quot;</span> : [0-9]<span class="pp">*</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2305.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="fu">expr</span> <span class="st">&quot;</span><span class="va">$input</span><span class="st">&quot;</span> : <span class="st">&quot;[0-9]*&quot;</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>ShellCheck found an <code>expr</code> command using <code>:</code> to
match a regex, but the regex is not quoted and therefore being treated
as a glob.</p>
<p>This means that if the problematic code is ever executed in a
directory containing a file matching <code>[0-9]*</code>, such as
<code>2021-reports</code> or <code>12 Angry Men [1957].mkv</code>, it
will be replaced be replaced and cause the command to error or
incorrectly match.</p>
<p>The regex should be quoted to avoid this, like in the correct
example.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>None</p>
<h3 id="related-resources">Related resources:</h3>
<ul>
<li>Help by adding links to BashFAQ, StackOverflow, man pages, POSIX,
etc!</li>
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